Generation and display of alphanumeric and other symbols



March 6, 1962 A. CHAIMOWICZ GENERATION AND DISPLAY OF ALPHA-NUMERIC ANDOTHER SYMBOLS 4 Sheets-Sheet 1 Filed Aug. 7, 1958 'x' vour:

"x" VOLTS A. CHAIMOWICZ 3,024,454

GENERATION AND DISPLAY OF ALPHANUMERI C AND OTHER SYMBOLS Filed Aug. 7,1958 4 Sheets-Sheet 2 March 6, 1962 AND"GATE March 6, 1962- A.CHAIMOWICZ 3,024,454

GENERATION AND DISPLAY OF ALPHANUMERIC AND OTHER SYMBOLS 4 Sheets-Sheet3 Filed Aug. '7, 1958 March 6, 1962 A. CHAIMOWICZ GENERATION AND DISPLAYOF ALPHANUMERIC AND OTHER SYMBOLS Filed Aug. '7, 1958 iOlI I03 4Sheets-Sheet 4 I 2y I373: lOly loay 131,

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D J m g y 44 64L) United States Patent 3,024,454 GENERATION AND DISPLAYOF ALPHA- N UMERIC AND OTHER SYMBOLS Adam Chaimowicz, London, England,assignor to Rank Precision Industries Limited, London, England, aBritish company Filed Aug. 7, 1958, Ser. No. 753,685 Claims priority,application Great Britain Aug. 13, 1957 8 Claims. (Cl. 340324) Thisinvention relates to the display upon the face of a cathode ray tube ofalpha-numeric and other symbols formed as a sequence of discrete lightdots and in particular to means for generating the waveforms controllingthe electron beam.

The expression characters will hereinafter he intended to include inaddition to alpha-numeric characters, other predetermined symbols, suchas punctuation marks and any patterns generally.

In the dot-sequential display of characters, the ultimate end of thecircuitry involved is the generation of coincident X and Y waveforms fordeflecting the beam of the cathode ray tube to the predetermined dotpositions defining a given character in conjunction with timedbeamswitching Z pulses applied to the beam-current control means of saidtube. In other Words, the cathode ray tube deflecting system requires ananalogue form of input.

Where said waveforms are determined by digital means, adigital-to-analogue converter must be resorted to in providing said formof input. Generation of characters by coding and decoding, as requiredby the digital approach to the problem, introduces certain complexitiesof circuitry and design which adversely reflect upon capital outlay,maintenance costs, and reliability generally, while aiming at relativefreedom from components drift, at least in the purely digital section ofthe arrangement. It would obviously be an advantage to generate thedeflecting signals in the formin which they are ultimately required.Analogue arrangements, on the other hand, place a heavy demand onconstancy of at least certain parameters depending on stability ofcomponents.

A primary object of the present invention is in fact to provide a methodof, and apparatus for, displaying characters in dot-sequential manner onthe face of a cathode ray tube, wherein the deflecting signals aregenerated in the analogue form required at the cathode ray tube whilemaintaining relative freedom from components drift, thus obviating theneed for coding and decoding.

A further object is to provide for easy changeability of the range andstyle of characters displayable.

The invention consists of an apparatus and method for selectivelydisplaying any one of a predetermined range of characters upon the faceof a cathode ray tube as a sequence of discrete light dots in positionsdefined by sequential pair of X and Y beam-deflecting voltages, whereinupon selection of a character the voltage pairs defining said characterare generated simultaneously in analogue form and stored for sequentialinterrogation and gating to the cathode ray tube deflection means.

Each voltage pair corresponds and is proportional to the Cartesiancoordinates with respect to a chosen pair of axes of the several dotsconstituting the character being generated and consists of an analoguevoltage applied to the X deflection means, hereinafter called the Xvoltage, and an analogue voltage coincidentally applied to the Ydeflection means, hereinafter called the Y voltage.

coincidentally with each voltage pair there is applied to the meanscontrolling the beam current of the tube a beam switching or bright-uppulse, hereinafter referred to as the Z voltage, it being understoodthat upon appli: cation of the Z voltage the beam of the cathode raytube 3,024,454 Patented Mar. 6, 1962 is switched on or intensified, thisleading to a bright dot appearing upon the face of the cathode ray tubein the position at the same instant defined by said voltage pair.

The generation of the coincident X and Y voltage pairs is eflected byfeeding an electrical signal, for example, in response to the output ofa computer device, via a function table or selection matrix, to ananalogue voltage generator capable of generating simultaneously all thevoltage pairs required for defining the character selected by saidfunction table.

Preferably, selection causes switchable magnetic core means exclusivelyassociated with the character selected to be switched from reset toactivated state, said core means being provided with windings in whichthe deflecting voltages are generated simultaneously upon switching.

Preferably, the analogue voltage generator is a core voltage generatorconsisting of an array of as many pairs of switchable magnetic cores asthere are characters to be displayed, each pair consisting of an X coreand a Y core, each core causing, upon switching from a reset condition,the generation of as many deflection voltages, respectively X and Yvoltages, as there are dots defining the particular character selected,said deflection voltages being generated each in a separate core windinghaving an integer number of turns and thus causing said voltages tooccur in quantized values. In both the X and Y set of cores thusdefined, windings associated with dots in the same sequential order-say,all the windings respectively generating the X co-ordinate from numberone dot-are connected in series. This means that in the X set of coresthere will be established the number one dot series, the number two dotseries and so on. Similarly for the Y set of cores.

The voltages thus generated are stored in a voltage memory from whichthey are interrogated by means including a succession of sequentiallyinterrogating pulses of equal amplitude initiated by a starting pulseand converted into sequential pairs of X and Y voltages for gating tothe cathode ray tube deflection means.

Preferably, the voltage memory includes storage condensers which areread out by interrogating pulses derived in response to a starting pulseoriginating from the analogue voltage generator, said starting pulseactivating a unit comprising basically a delay line and a group of pulseshapers.

Said interrogating pulses are further employed in conjunction with atleast a portion of the analogue output read out from the voltage memoryto provide a train of bright-up pulses always equal in number to thenumber of dots defining the selected character.

Preferably, at least a portion of the interrogating pulses output isadapted to be gated towards the beam-current controlling means of thecathode ray tube upon coincidence with the co-operating portion of saidanalogue output read out from the voltage memory.

The X, Y, and Z voltages thus genera-ted and defined may be used tocontrol any number of additional cathode ray tubes for the purpose ofproducing one or more duplicate displays.

The invention will now be described by way of ex- 18 dots, the letter B(FIG. 2) similarly by the overlapping of 37 dots, and that the full stop(FIG. 3) consists of a single dot. The position of each dot is definedby an X voltage and a Y voltage. When the required pairs of X and Yvoltages are sequentially applied to the deflection system of a normaltype cathode ray tube, the electron beam will be shifted sequentially tothe positions defined by the successive X and Y pairs, in the ordershown by the numbering of the dots in FIGS. 1, 2, and 3, thus formingthe selected character.

The beam switching Z voltage hereinbefore referred to is adapted toswitch on the electron beam when the first dot position has beenselected, extinguish the electron beam after a predetermined timeinterval, and switch on the beam again when the second dot position hasbeen selected, the sequence being continued until after the exhibitionof the final dot, when the beam is extinguished until it is required forthe formation of the next character.

With reference to FIG. 4, character code in the form of a combination ofelectrical pulses is fed from any computer device source to a functiontable 1 which converts the coded pulses into switching pulses toinitiate the generation of the character represented by the inputpulses.

This function table or selection matrix is constructed according toknown principles, and is of the type some out of m into one out of n,where m is the number of digits or pulses per character in the code usedin the input to the invention, and n is the total number of charactersavailable in a given embodiment. Thus if the embodiment being consideredis to be fed with 6-digit code, and has to generate any of 64predetermined characters, the function table will be of the type someout of 6 into one out of 64." It will therefore be supplied with 64output wires 2 each one corresponding to a character, and with 6code-input wires 3. Each of 64 out of all the possible modes ofactivating the input wires will be significant, and will signify acharacter, and will cause the output wire corresponding to thatcharacter to become activated, i.e. to carry an electrical pulse. Thereis provided an additional input wire 4 carrying a parity signal, whichin conjunction with samples of the signals carried by the output wires 2and of signals carried by the input wires 3, by means of known logicaldevices 5, 6, 7, and 8 shown dotted in FIG. 1, will cause that part ofthe apparatus subsequent to the inhibitor 9 to become inoperative ifthere should be present at its input a non-significant, incomplete orotherwise erroneous signal, or unless one and only one of the outputwires 2 should be activated in response to a single input code-group.

In actual fact, unit 5 is adapted to produce an output pulse when oneand only one of its inputs originating from wires 2 is activated, and inFIG. 4 has been captioned one input at a time OR gate." Similarly unit 7is adapted to produce an output pulse when and only when the binarypulse combination on wires 3 extended thereto produces parity inconjunction with the parity signal fed on wire 4. In FIG. 4 has beencaptioned Parity gate. In normal circumstances, unit 6, which in FIG. 4is captioned Reverse AND gate, would receive an input pulse from unit 7coincidentally with an input pulse from unit 5, and as long as thiscondition is maintained it is arranged that no output pulse shall issuefrom unit 6. An output pulse is however produced when coincidence ofinputs fails. The output pulse from unit 6 upon a failure havingoccurred is adapted to activate inhibitor unit 9 disabling unit 13, andto send out a reset signal after a time delay governed by unit 8, saidsignal resetting both the core voltage generator and the voltage memory.

The function table output wires 2 are fed to a core voltage generator 10which is shown in detail in FIG. 5. This generator consists of a numberof ring shaped cores composed of rectangular B-H loop material such asferrite material, each wound with a specified number of windings, eachwinding having a specified number of turns. Two cores are provided foreach character, one to supply voltages corresponding to the X voltages,and one to supply voltages corresponding to the Y voltages of thatcharacter. In addition, each core carries a winding for the input pulsesand a winding to enable its magnetic state to be re-set after thegeneration of a character is completed. Further, one set of cores,either that corresponding to the X voltages or that corresponding to theY voltages, carries on each member an additional winding to provide avoltage hereinafter referred to as the starting pulse whose function isdescribed later.

Referring to FIG. 5, four pairs of cores are shown out of the 64 pairsactually used in the embodiment being considered and corresponding to 64different displayable characters. The action of the core voltagegenerator will be described with reference to the pair of cores marked22 and 23. For simplicity, not all of the windings are shown. Thoseillustrated are: 24 the input winding of core 22; 25 the reset windingof core 22; 26 the starting pulse winding; 1x, 2x, 3x and 37x some ofthe X voltage windings; 27 the input coil of core 23; 28 the reset coilof core 23; 27 and 35 some of the Y voltage windings; 29 and 30 shortinglinks taking the place of windings where zero voltages are required. Ifnow the character corresponding to cores 22 and 23 is presented in codeat the input wires 3 (FIG. 4) it will so activate the function table 1,that the wire 31 (FIG. 5) will carry a pulse. This pulse, passingthrough coils 24 and 27 will alter the magnetic state of cores 22 and 23thereby generating pulses in the other windings on these cores. Thepulses generated in the reset windings 25 and 28 are not used, thestarting pulse in winding 26 is used as described hereinafter and thepulses in the remaining windings are given magnitudes corresponding andproportional to the required X voltages and Y voltages by suitablyarranging an integer number of turns in each coil, the integer numberleading to quantizing of voltages. The maximum number of dots in anycharacter in the present embodiment will be taken to be 37 so that eachcore carries not more than 40 windings of which not more than 37 areused for the generation of X and Y voltages.

In both the X set of cores and Y set of cores, windings having the sameorder number, ie corresponding to character elements occupying the samenumerical position in the scanning sequence, are connected in series,thereby providing a single output wire for the impulse defining one orother co-ordinate of the element occupying that numerical position inany required character. This is possible since the nature of the coresused is such that a coil on an unswitched core possesses an extremelylow impedance in comparison with either the impedance of a coil on aswitched core, or with that of the subsequent unit, which is the voltagememory.

Referring again to FIG. 4, the X and Y voltage pulses are transmittedvia 2x37 core voltage generator output wires 11 to the voltage memory12, which is shown in detail in FIG. 6.

Refening to FIG. 6 in respect of the X coordinates and in conjunctionwith a similar assumed layout for the Y coordinates, some or all of thewires 101x, 102x, 103x 137x, and 101y, 102 103 137 which are the samewires as the wires 11 in FIG. 4, will carry pulses consequent upon theaction of the core voltage generator 10 (FIG. 4) already described. As aresult, some or all of the condensers 201x 237x, and corresponding Ycondensers will become charged, each via one of the reading-in diodes301x, 302x 337x and corresponding Y diodes, to a voltage adapted to bevirtually equal to the peak voltage of the pulse applied to that diode.

The condensers 201x, 202x 237x, and corresponding Y condensers areconnected in the grid circuits of cathode-followers 401x, 402x 437x, andcorresponding Y cathode-followers. Thus voltages to which the condensersare charged become efiective in the cathode output of these valves.Since the pulses from the core voltage generator (FIG. 4) aresimultaneous, all the condensers in the voltage memory charge to theirvarious voltages simultaneously, said voltages being each simultaneouslyduplicated in the output of associated cathodefollower.

For the spot-sequential presentation of the character on a cathode raytube screen, the voltages are required in sequential pairs, first, thatfrom 201x together with that from corresponding Y condensers forming anX and a Y voltage respectively; next, that from 202x together with thatfrom corresponding Y condensers; and so on until the number of pairsnecessary to form the required character have been supplied to thecathode ray tube. In this embodiment of the invention this is achievedby supplying to the voltage memory via the set of wires 101a, 102a 137aa train of sequentially interrogating pulses of the constant amplitude.The first of these pulses appears on wire 101a and is followed at shortequal intervals by pulses on wires 102a 137a, until the interrogation ofthe voltage memory is completed. These sequentially interrogating pulsesare applied each to one input wire of each of two AND" gates, said gatescomprising an X AND gate and a Y AND gate, the other input wire of eachsuch gate being connected to the cathode of the appropriate valve of thesaid 401x, 402x 437x, and corresponding Y valves in such a way that 201xand corresponding Y condenser are interrogated by the first pulse, 202xand corresponding Y condenser by the second, and so on. When aninterrogating pulse arrives at the AND gate connected to a valve havinga charge on its associated condenser, and therefore a correspondingvoltage across its cathode resistance, there will be an output from thatAND gate corresponding to and virtually equal to the peak value of thepulse which originally charged that condenser.

Normally the branch of the AND gate connected to the cathode resistanceas shown in FIG. 6 has its diode biased in the forward direction, sothat in the absence of a charge on the associated memory condenser saiddiode is conducting. The other branch at this stage is not activated andconsequently there is no output from the gate.

Upon reading-in of a deflection voltage from the core generator, a PD.(i.e., potential difierence) appears across the cathode resistance whichtends to make the appertaining diode non-conducting to an extentproportional to the value of said P.D. Until the diode of the otherbranch is left in the conducting state, its internal resistance is solow that it acts as a shunt across the output of the gate. When,however, it is made non-conducting on being pulsed in the reversedirection by the interrogating pulse, the output of the gate is madeavailable for extending it to the cathode ray tube deflection means.

The output of the voltage memory will therefore consist of voltage pairsin rapid sequence, one member of each pair being an X voltage and theother a Y voltage, each pair being suitably proportioned and scaled todefine the position of one element of the required character on the faceof the cathode ray tube. These outputs appear on some or all of thewires 501x, 502x, 503x 537x and 5013 502 503 5373 Referring again toFIG. 4, the sequentially interrogating pulses above mentioned are seento be derived from the unit numbered 13. This unit consists of a delayline and a group of 38 pulse shapers 1a, 2a, 37a 38a, shaper 38aproducing the reset pulse, said shapers being of the same generalfunctional type as for instance described at page 481 of Radio and RadarTechnique by A. T. Starr, published by the Pitman Publishing Company.Said unit is fed, via a further shaper 14, with the starting pulsementioned above derived from core voltage generator 10. The startingpulse is a voltage pulse and shaper 14 converts it into a current pulse,which as it proceeds down the delay line initiates: a pulse output fromeach of the shapers 1a 37a in turn, these pulses forming the sequentialinterrogating pulse train. Unit 13 further provides a pulse from 38awhich is used to reset both the core voltage generator 18, by causing areset pulse to reset the core which originally sent out the start pulseat the beginning of generation of one character, and the voltage memory12., by causing the individual memory condensers to discharge, forinstance, through a constant-current discharge device includingdischarge diodes 601x, 602x, 637x through wire 32 (FIG. 6) andcorresponding Y discharge diodes. This is effected at the end of thegeneration of the one character selected in readiness for the generationof the next character to be selected.

The pulses resulting in the output of the voltage memory 12 from theapplication of the sequentially interrogating pulses are taken in twogroups, all of the X voltages going to an OR gate 15 and all of the Yvoltages to another OR gate 16 (FIG. 4). The output of these gates arethe sequential pairs of X and Y voltages: which are fed to thedeflection system of a cathode ray tube or tubes.

It should be observed that for elfective gating the amplitude of thesequential interrogating pulses must be greater than the highestpossible voltage read-in in any one memory condenser.

The method used in this invention for forming the brighten-up pulses orZ voltages will now be described. In the core voltage generator 10, theX cores, for eX- ample are provided with a sufficient number of windingturns in respect of each co-ordinate to generate a voltage of the orderof 5 volts in excess of that required for coordinate determination. Thishas no effect on the shape of the character, but ensures that there isan output voltage for every dot of the total defining the characterselected from OR gate 15. The output from this gate is extended to aclipper 17, of the general type as shown for instance at page 467 of theabove reference, which produces a train of equally spaced pulses ofequal amplitude. A portion of the train of pulses from the shapers 1a,2a, 3a 37a is fed to an OR gate 18 producing at its output a pulse trainon a single wire. This train is fed to a shaper 19, of the same generaltype as that shown at page 481 of the above reference, which produces inits output a sequence of 37 deferred pulses. This train and the outputfrom the clipper 17 are each fed to one of the two inputs of the ANDgate 20. The output from the shaper 19 will consist, for everycharacter, of 37 consecutive pulses. If, however, the character underconsideration has only 18 elements as in the example of the numeral 7quoted above, the output from the clipper 17 will consist of 18 pulses.Thus the output from the AND gate 20 in this case would consist of 18pulses only, and in general will always consist of a number of pulsesequal to the number of dots in the character being generated. Thesepulses are fed to an amplifier 21 where they are sufiiciently raised inlevel to enable them to switch on the beam of a cathode ray tube. Theoutput of this amplifier is the pulse train previously referred to asthe Z volts. The shaper 19 is so arranged that each pulse in the Z voltstrain commences later and finishes earlier than the corresponding pulsein the sequence of X and Y voltage pairs. Hence the beam of the cathoderay tube will not be switched on while it is moving towards or leaving aposition defined by one of the X and Y voltage pairs.

The logics associated with the generation and timing of the Z pulsesensures, therefore, that these bright-up pulses are made available atthe cathode ray tube only coincidentally with one dot and for a durationslightly less than that, say, of the X co-ordinate of said dot.

The operation of the invention from selection of a given character todisplay thereof in dot-sequential form upon the face of a cathode raytube will now be traced with reference to the drawings.

It is assumed that the binary code combination as signed to the letter Ahas appeared upon wires 3 of FIG. 4, the letter A forming the output ofa computor device at one particular instant of time. Function table 1,being thus activated, instantly selects one of its 2 unique outputlines, 11 being the number of lines on which the binary input code isformed. Assuming that the first of the output lines bearing the generalreference 2 corresponds to the letter A, activation of said line resultsin a pulse being available thereon. The line is connected to the inputwinding of the X core and the Y core generating character A. Thus the Acores are switched simultaneously from reset to activated state inresponse to selection of the A line.

Upon simultaneous switching of the A cores, X and Y voltage pairs aresimultaneously generated and stored each in a pair of memory condensers.At the same time either the X or the Y core causes the regeneration of astart pulse from which a sequential pulse generator is activated for thepurpose of interrogating sequentially the pairs of memory condensers andproducing step by step simultaneous X and Y waveforms in the timesequence required at the cathode ray tube for defining the letter A.

As the coordinates are being generated, say, the X co-ordinate voltages,a portion thereof is utilized to condition a gate for allowing a.portion of the sequential pulse output to be gated to the cathode raytube for the purpose of intensifying the beam of said tube only when adot occurs.

At the end of its interrogating cycle, the sequential pulse generatorproduces a reset pulse which causes the cores and the memory condensersassociated with the letter A to be reset. The operation described takesonly a few microseconds and the device is ready to respond to theselection of another character.

One of the aims in the conception of the method disclosed has been toprevent drift in components aifecting the shape of any character. Tothis end it has been arranged for all the co-ordinates to be generatedsimultaneously so that any drift involves all co-ordinates in a nearlyuniform manner and safeguards the shape of the character. The generatingmeans actually preferred is a core voltage generator in which, bysuitable switching arrangement, the output pulse may be closely definedin level and made independent of temperature changes affecting thephysical constants of the core. Said arrangement is also adapted toensure that the output voltage pulses have a waveform with asubstantially flat top portion. This feature in conjunction withjudicious choice of output pulse duration in relation to the timeconstant of the associated memory condenser ensures that each condensercharges up to a substantially constant predetermined level despite asmall drift in the time constant of the charging circuit.

Thus the analogue approach to the problem of character generation,inherently simpler, has been pursued while safeguarding stability ofoperation. Another notable advantage achieved by the invention is theease with which any one character may be replaced by simple substitutionof the X and Y core pair defining said character without the need forpainstaking adjustments. The X core and the Y core may in fact bearranged in the form of separate plug in units or even in a combinedplug-in unit. The importance of this facility is obvious when outputs invarious languages and symbols have to be accommodated.

This in combination with the ease with which the maximum number of dotsdefining any given character may be increased-either to improvedefinition of display or to generate unusually complex patternsleads toextreme versatility allied with simplicity in the presentation ofpredetermined visual information upon a cathode ray tube.

It will be appreciated by those skilled in the art that the functions ofthis invention as described herein and illustrated in the accompanyingdrawings have been treated in a simplified fashion, in the mannercustomary with apparatus of this nature. Thus, while all of theessential components have been described and illustrated it may bedesirable or necessary in practice to include known devices such asamplifiers, transformers and the like in the inter-connection linksbetween the several units in order to modify power levels and to matchimpedances; and/or to modify the transient responses of certaincomponents by the use of damping resistors; and/or to use more than onevalve, or a transistor or transistors instead of a valve, where onevalve is shown. Furthermore, the number of cores per character may beother than two; for example, one core may carry all the windingsrequired for the formation of a single character, or as many cores mightbe provided as the number of windings required, or any intermediatenumber of cores might be employed.

I claim:

1. A waveform generator comprising switchable mag netic means, aplurality of windings upon said magnetic means, means for switching themagnetic state of said magnetic means to induce analogue voltages insaid windings proportional to the number of turns in each winding,analogue storage means for storing each individual voltage,interrogating means for sequentially sampling said storage means andmeans for sequentially gating the storage contents to a circuit for theutilization of the step by-step wave form thus generated, whereby eachinstantaneous element of the waveform is represented by an analoguequantity throughout the generator.

2. A Waveform generator for producing simultaneously X and Y deflectionwaveforms and Z bright up pulses for dot sequential cathode ray tubedisplay of graphical symbols comprising an X set of switchable magneticcores, a Y set of switchable magnetic cores, one core of the one set andone core of the other set forming an X-Y pair for defining one symbol, apinrality of windings on each core, means for switching any one corepair to induce analogue voltages in the windings associated therewithproportional to the number of turns in each winding, an analogue storefor each induced voltage, each voltage representing one coordinate ofone dot, interrogating means for sampling said stores in sequentialmanner and for causing Z pulses, and means for sequentially gating thecontents of said stores whereby step-by-step X and Y wave forms are madeavailable to the X and Y deflection means of a cathode ray tube and Zbright up pulses are made available to the beam controlling means of thetube, said X and Y waveforms in conjunction with said Z bright up pulsesenabling the symbol corresponding to the switched core pair to bedisplayed upon the face of the cathode ray tube.

3. A waveform generator as claimed in claim 2, wherein the interrogatingmeans includes a sequential pulse generator and a Z pulse is producedwhenever a pulse from the sequential pulse generator coincides with thegating of the contents of a store.

4. A system for selectively displaying any one of a predetermined rangeof graphical symbols in response to coded electrical input combinationrepresentative of the symbol selected comprising decoding means yieldinga unique electrical output in response to said combination, generatingmeans for simultaneously generating a set of analogue voltage pairs inresponse to said unique output, analogue storage means for storing saidvoltage pairs, interrogating means for sampling sequentially thecontents of said storage means, and means whereby one member of eachvoltage pair stored is sequentially gated from said storage means to theX deflection means of a cathode ray tube and the other member to the Ydeflection means of said cathode ray tube and whereby the symbolselected is displayed as a succession of light dots on the face of saidtube, the beam of the cathode ray tube being swept only to the positionscorresponding to the coordinates of said dots.

5. A system for selectively displaying any one of a predetermined rangeof graphical sysmbols in response to coded electrical input combinationrepresentative of the symbol selected comprising decoding means yieldinga unique electrical output in response to said combination, generatingmeans including switchable magnetic core means provided with windingsfor simultaneously generating therein a set of analogue voltage pairsupon switching of said core means in response to said unique output,analogue storage means for storing said voltage pairs, interrogatingmeans for sampling sequentially the contents of said storage means, andmeans whereby one member of each voltage pair stored is sequentiallygated from said storage means to the X deflection means of a cathode raytube and the other member to the Y deflection means of said cathode raytube and whereby the symbol selected is displayed as a sucession oflight dots on the face of said tube, the beam of the cathode ray tubebeing swept only to the positions corresponding to the coordinates ofsaid dots.

6. A system for selectively displaying any one of a predetermined rangeof graphical symbols in response to coded electrical input combinationrepresentative of the symbol selected comprising decoding means yieldinga unique electrical output in response to said combination, generatingmeans including two switchable magnetic cores provided with windings forsimultaneously generating therein a set of analogue voltage pairs uponsimultaneous switching of said two cores in response to said uniqueoutput, analogue storage means for storing said voltage pairs,interrogating means for sampling sequentially the contents of saidstorage means, and means whereby one member of each voltage pair storesis sequentially gated from said storage means to the X deflection meansof a cathode ray tube and the other member to the Y deflection means ofsaid cathode ray tube and whereby the symbol selected is displayed as asuccession of light dots on the face of said tube, the beam of thecathode ray tube being swept only to the positions corresponding to thecoordinates of said dots.

7. A system as claimed in claim 4, wherein windings producing a voltagecorresponding to identical dot positions throughout said range ofgraphical symbols are connected in series, the impedance of the windingsupon unswitched cores in any series being negligible.

8. A system for selectively displaying any one of a predetermined rangeof graphical symbols in response to coded electrical input combinationrepresentative of the symbol selected comprising decoding means yieldinga unique eelctrical output in response to said combination, generatingmeans including two switchable magnetic cores provided with windings forsimultaneously generating therein a set of analogue voltage pairs uponsimultaneous switching of said two cores in response to said uniqueoutput, analogue storage means including pairs of capacitors for storingsaid voltage pairs, interrogating means including a sequential pulsegenerator for sampling sequentially the contents of said storage means,means whereby one member of each voltage pair stored is sequentiallygated from said storage means to the X deflection means of a cathode raytube and the other member to the Y deflection means of said cathode raytube, and means whereby a beam bright up pulse is produced whenevercoincidence occurs between a pulse from the sequential pulse generatorand a voltage gated from said storage means and whereby the symbolselected is dis played as a succession of light dots on the face of saidtube, the beam of the cathode ray tube being swept only to the positionscorresponding to the coordinates of said dots.

High-Speed Number Generator Uses Magnetic Memory Matrices, An Wang, May1953, p. 200, Electronics.

